Electrosurgical endoscopic instruments and methods of use

ABSTRACT

Endoscopic surgical instruments are provided that have bipolar electrodes on opposing movable members for passing a high frequency current through tissue for simulataneously severing or manipulating the tissue and causing hemostasis of the tissue. An electrically insulating material is interposed between the movable members so that the electrodes are spaced apart from 0.002 to 0.050 inches and the current passes between the opposing electrodes through the tissue. Methods of endoscopically achieving hemostasis while simultaneously, manipulating and cutting tissue are also provided. Use of a constant voltage high frequency power supply to deliver current to the tissue to cause hemostasis is described in conjunction with those methods.

This is a continuation of application Ser. No. 08/257,065, filed Jun. 9,1994, entitled BI-POLAR ELECTROSURGICAL ENDOSCOPIC INSTRUMENTS ANDMETHODS OF USE, now abandoned, which is a continuation of Ser. No.07/877,704 filed May 1, 1992 now U.S. Pat. No. 5,330,471, which is acontinuation-in-part of commonly assigned and U.S. patent applicationSer. No. 07/711,920, filed Jun. 7, 1991, now abandoned.

This invention relates to hemostatic electrosurgical instruments, andparticularly to improved bi-polar electrosurgical instruments formanipulating and causing hemostasis of tissue during endoscopic surgicalprocedures.

BACKGROUND OF THE INVENTION

In "open" surgical procedures, the surgeon gains access to work insidethe body by cutting large incisions through the body wall, thenstretching the overlying tissue apart to provide visibility and room tomanipulate his hands and instruments. Vital structures are generallyheld away from the surgical site and shielded from instruments by beingcovered with cloth pads. The surgeon can touch and manipulate thetissues. As the surgeon manipulates, cuts and dissects tissues, hecontrols the resultant bleeding by blotting or suctioning away theaccumulating blood, enabling him to see the bleeding vessels and clampand tie them off.

The creation of a large opening in the patient's body tissue greatlyincreases the risk of surgery to the patient's health, by increasing theprobability of complications. Those complications can arise not onlyfrom treatment of the target tissue, i.e., that tissue necessitating thesurgery, but also from the trauma caused to adjacent tissue in creatingan opening providing the surgeon with access to the target tissue. Oncethe internal tissue is operated upon, the surgeon faces thetime-consuming task of closing up the surgical site. In addition, thepatient may require extensive post-operative care and an extensivehospital stay.

Development of the endoscope, a miniaturized television camera that isinserted through a puncture wound in the body wall to provide a videoimage of the inside of the body cavity, has enabled surgeons to performsurgery using specially designed surgical instruments that are insertedthrough other small puncture wounds. Some previously known devices havebeen constructed that enable a surgeon to operate on internal tissuewhile viewing manipulation of the instrument through an endoscope. Onesuch device is described in Falk, U.S. Pat. No. 4,994,024. Suchpreviously known endoscopic instruments have several disadvantages,especially the inability to effectively stem blood flow from incisedtissue.

Endoscopic surgery no longer requires cutting a large gaping incisionthrough the body wall, and permits patients to undergo some majorsurgeries practically pain-free, with little or no post-operativehospital stay. However, in performing endoscopic surgery the surgeonforgoes manual access to the tissues being operated upon. In doing so,he gives up his traditional means of controlling bleeding by clampingand tying off transected blood vessels. Consequently, in endoscopicsurgery it is important that tissues that are cut must not bleed.

Hemostatic surgical techniques are known for reducing the bleeding fromincised tissue during open surgical procedures, i.e., where overlyingbody tissue is severed and displaced to gain access to internal organs.Such techniques include electrosurgery, that is, passing a highfrequency or radio frequency current through the patient's tissuebetween two electrodes for cutting and coagulating the blood vesselscontained within the tissue. The current passing through the tissuecauses joulean (ohmic) heating of the tissue as a function of thecurrent density and the resistance of the tissue through which thecurrent passes. This heating dehydrates the tissues and denatures thetissue proteins to form a coagulum which seals bleeding sites, so thatthe body's own collagen is reformed as a glistening white layer on thecut surface, sealing the tissues against bleeding.

Heretofore, endoscopic electrosurgical techniques have been limitedprimarily to monopolar devices. Previously known monopolarelectrosurgical instruments employ a small electrode at the end of ahandle in the surgeon's hand and a large electrode plate beneath and incontact with the patient. Only one of the two electrodes required tocomplete the electrical circuit is manipulated by the surgeon and placedon or near the tissue being operated on. The other electrode is thelarge plate beneath the patient. A power supply impresses high frequencyvoltage spikes of thousands of volts between the two electrodes of theelectrosurgical instrument, sufficient to cause arcing from the smalloperating electrode the surgeon holds to the most proximate tissues,then through the patient to the large electrode plate beneath thepatient. In the patient, the electrical current becomes converted toheat; hottest in the tissues immediately below the small hand-heldelectrode where the currents are most concentrated. Devices, such as theforceps Model No. A5261, and electrode Model No. A5266, available fromOlympus Corporation Medical Instrument Division, Milpitas, Calif., arerepresentative of such monopolar instruments.

A principal disadvantage of monopolar electrocautery is that currentflows completely through the patient. These high voltage electricalcurrents may arc from the small electrode to nearby non-targeted vitalstructures, or may follow erratic paths as they flow through thepatient's body, thereby causing damage to tissues both near and at somedistance from the electrode.

While monopolar devices have proven useful in open surgical procedures,where the surgeon is able to view the effects of the current arc, theproblems encountered in open surgical procedures become even moreimportant in endoscopic surgical applications. In particular, when usinga monopolar device endoscopically, the surgeon's view of the electricarc generated by the instrument is restricted by the limited field ofview provided by the endoscope. Consequently, aberrant current arcs--theexistence of which the surgeon may not even be aware--can cause deeptissue necrosis and inadvertent damage to adjacent tissue masses.

The foregoing limitation has proved especially dangerous for surgeriesperformed in the abdomen, and in the vicinity of the peritonea and bowelwall. Practical experience has established that aberrant current arcsgenerated by endoscopic monopolar devices can cause perforation of theadjacent bowel wall when used on abdominal tissue masses. While suchdamage typically is not apparent to the surgeon during the procedure, itmay later be manifested as peritonitis, which results in death in asmany as 25% of all such cases.

Bipolar electrosurgical devices for open surgical procedures are knownto enable the surgeon to obtain hemostasis in precise local areaswithout also heating and causing undesirable trauma to adjacent tissue.Bipolar devices have two electrodes closely spaced together so thatcurrent flow is confined to the tissue disposed between the electrodes.Heretofore, such instruments have had limited use in endoscopicapplications because of the inherent problem of electrically isolatingthe high voltage electrodes while providing an instrument small enoughfor use with conventional trocar tubes--typically 5 to 10 mm indiameter. One such device is described in Tischer U.S. Pat. No.4,655,216. The complicated structure of the device described in thatpatent illustrates the difficulty encountered in providing the requisiteisolation of the electrodes. A second such device is the Olympus ModelO5127 bipolar endoscopic forceps, available from Olympus CorporationMedical Instrument Division, Milpitas, Calif.

A further disadvantage inherent in all previously known monopolar andbipolar electrosurgical devices is that of coagulum buildup on theworking surfaces of the device. Previously known power supplies used inelectrosurgical applications have generally provided high voltage-lowcurrent power outputs, which poorly match the impedance of the tissueover the range of conditions typically encountered in electrosurgery.This mismatch, in combination with the arcing characteristic ofpreviously known instruments, leads to charring of the tissue andexcessive coagulum buildup on the instrument surfaces.

Yet another difficulty encountered in endoscopic surgery is the limitedrange of motion available to the surgeon at the surgical site. Inparticular, because of the relatively small incision through which theinstruments are inserted for endoscopic procedures, the surgeon's rangeof movement of the instrument is greatly restricted.

It would therefore be desirable to provide bipolar electrosurgicalinstruments for hemostatically severing or manipulating tissue inendoscopic surgical procedures that overcome these disadvantages of suchpreviously known instruments. Such instruments would enable a largenumber of operations to be carried out endoscopically, thereby reducingthe need and risk of open surgical procedures.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide improved endoscopic surgical instruments, the existence of whichwill expand the field of endoscopic surgery. In particular, theexistence of instruments providing heretofore unavailable functions,ease of use, and enhanced safety will encourage the conversion of anumber of surgeries--now carried out as open procedures--to endoscopicprocedures. Such conversion from open to endoscopic surgeries willreduce the risk of surgery to the patient, reduce the trauma to adjacenttissue from the surgery, and enable faster post-operative recovery.

It is, therefore, an object of this invention to provide bipolarelectrosurgical instruments for endoscopic surgical procedures that havea simple structure, yet provide the necessary electrical isolation ofthe bipolar electrodes. The bipolar devices constructed in accordancewith the present invention confine current flow to the tissueimmediately adjacent to the electrodes of the instrument. Thus, thesedevices significantly reduce the likelihood of creating aberrant currentarcs that can perforate the peritonea or other adjacent tissue. Theoverall safety of endoscopic procedures is thereby enhanced, permittinga larger number of surgeries to be performed endoscopically.

It is another object of the present invention to provide bipolarendoscopic instruments which experience little sticking or coagulumbuildup during extended use. In accordance with the present invention,endoscopic bipolar instruments are employed in conjunction with powersupplies providing load-independent substantially constant voltageoutput. Voltage and current ranges are provided that significantlyreduce coagulum buildup and charring of tissue.

It is another object of this invention to provide bipolarelectrosurgical instruments that provide the surgeon with a high degreeof maneuverability of the instrument once it is located at the surgicalsite. The instrument constructed in accordance with the principles ofthis invention therefore includes means for rotating the working end ofthe instrument while it is positioned at the surgical site.

These and other objects are accomplished in accordance with theprinciples of the present invention by providing bipolar electrosurgicalinstruments having an elongated barrel for insertion through a trocartube at the patient's skin, a working end disposed on the distal end ofthe elongated barrel, and handle members for actuating the instrument.Means are provided near the proximal end of the barrel for rotating theworking end of the instrument. The instrument includes means forconnecting the instrument to a power supply to energize the electrodesat the working end.

Bipolar instruments constructed in accordance with the present inventionhave a working end that comprises bipolar electrodes and movable memberscapable of performing any of a number of functions. A layer ofinsulation is provided on one or both of the mating surfaces of themovable members to maintain electrical isolation of those components. Aworking end constructed in accordance with the present invention maycomprise a scissors-like cutting instrument which simultaneously causeshemostasis of tissue and mechanically severs that tissue in a continuousmanner, a dissector-like instrument for grasping and achievinghemostasis of tissue, or a dissector for blunt dissection, whichhemostatically separates tissue.

In a first embodiment, the movable members of the working end comprisescissor members having opposing mating surfaces. Electrodes associatedwith the scissor members conduct high frequency current to tissue tocoagulate the blood vessels extending through the tissue while cuttingedges of the scissor members mechanically sever the tissue. A layer ofinsulating material is disposed on at least one of the mating surfacesof the scissor members so that the electrically active portions of thescissor members do not contact each other at any point during operationof the instrument. Thus, current flows through tissue between thescissor members, but short circuits, which would terminate hemostasis,do not occur. With this arrangement, hemostasis and cutting occurs in acontinuous manner along tissue disposed between the scissor members,thereby providing a smooth and precise surgical cut.

Another embodiment of the invention comprises an endoscopic hemostaticdissector, wherein the movable members comprise opposing jaws forsimultaneously grasping and causing hemostasis of the tissue. Like thefirst embodiment, the jaw members include shank portions formingopposing mating surfaces. A layer of insulating material is disposed onat least one of these mating surfaces so that electrically activeportions of the members do not contact each other during operation ofthe instrument.

The movable members of either embodiment may be curved so that the tipsof the members lie in a plane parallel to, and separate from, thelongitudinal axis of the elongated barrel. This feature enhances thesurgeon's view of the working end of the instrument, thereby providinggreater precision in manipulating the tissue at the operative site.

The present invention also includes methods of endoscopically usingbipolar electrosurgical instruments to simultaneously grasp ormechanically sever tissue while thermally reforming the collagen of thetissue to seal the tissue against bleeding. For endoscopicallyperforming surgery on a patient's internal tissue using a bipolarelectrosurgical instrument in combination with a power supply having aselectable substantially constant voltage load-independent output, theinstrument having an elongated barrel, a working end comprisingelectrodes, and means for actuating the working end, the methods includethe steps of:

(a) connecting the electrodes of the bipolar electrosurgical instrumentto the power supply;

(b) incising the patient's tissue with a trocar or similar device tocreate a small opening;

(c) inserting the working end and elongated barrel of the bipolarelectrosurgical instrument through a trocar tube so that the working endis disposed proximal to the internal tissue; and

(d) operating the actuating means to simultaneously manipulate and causehemostasis of the tissue.

Further steps of the methods include the step of setting the powersupply to provide a voltage across the electrodes in the range of 10 to120 volts (RMS) and a frequency in the range of 100 kHz to 2 MHz. Themethods further include the use of alternating-current voltage waveformshaving a crest factor--ratio of peak voltage to root-mean-square (RMS)voltage--near unity.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the invention will beapparent upon consideration of the following detailed description, takenin conjunction with the accompanying drawings, in which like referencenumerals refer to like parts throughout, and in which:

FIG. 1 is an elevated perspective view of an illustrative embodiment ofthe instrument of the present invention;

FIG. 2 is an elevation cross-sectional side view of the instrument takenalong the line 2--2 of FIG. 1, in which an intermediate portion of theelongated barrel has been omitted for clarity;

FIG. 3 is an exploded perspective view of the working end of theinstrument taken along line 3--3 of FIG. 1;

FIG. 4 is an exploded perspective view, similar to FIG. 3, of analternate embodiment of the working end of the instrument;

FIGS. 5A and 5B show, respectively, open and closed enlargedcross-sectional views of the working end of the instrument shown in FIG.2;

FIG. 6 is a cross-sectional view of an alternate embodiment of thescissors-like working end of the present invention;

FIGS. 7A and 7B, respectively, are cross-sectional views, similar toFIGS. 5A and 5B, showing a dissector embodiment of the working end ofthe present invention; and

FIG. 8 is a plan view of an alternate embodiment of the dissectorembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a bipolar electrosurgical instrument 10 forperforming endoscopic surgical procedures is described. While aninstrument constructed in accordance with the principles of the presentinvention may include any of a variety of severing or grasping membersat its working end 11, the illustrative embodiment of FIGS. 1 and 2includes scissor-like shearing members for simultaneously severing andcausing hemostasis of a patient's tissue.

Instrument 10 includes actuating means comprising handle members 12 and13 joined for relative movement at pivot 14, tubular elongated barrel15, and working end 11. Drive rod 16 disposed in elongated barrel 15 haselectrical terminals 17 that are connected to movable members 18 and 19of working end 11 to provide an electrical potential therebetween.

Handle member 12 has a pistol-like configuration, including a bodyportion 20 having a longitudinal bore 21 and a portion defining a holefor one or more fingers. Handle member 12 may be made of a light-weightrigid material, for example cast aluminum. Elongated barrel 15 comprisesa tube having a proximal end mounted in body portion 20 and a distalportion forming part of working end 11. The proximal end of elongatedbarrel 15 is mounted in bore 21 of body portion 20 so that elongatedbarrel 15 can be rotated about its longitudinal axis. Elongated barrelmay consist of a rigid structural material, for example a stainlesssteel alloy, e.g., SS 304, and may include a coating of abherentmaterial, such as Teflon, on its exterior surface.

Knurled rotation knob 22 is mounted on a portion of elongated barrel 15disposed in body portion 21, so that it projects through slots 23intersecting bore 21 of body portion 20. Rotation of knurled knob 22causes elongated barrel 15 to rotate about its longitudinal axis,thereby also rotating working end 11.

Body member 20 has bore 24 communicating with bore 21 so that set screw25 disposed in bore 24 engages elongated barrel 15 substantiallyperpendicularly to the longitudinal axis of the barrel. Set screw 25 haslocking knob 26 at one end and teat 27 at the other end to engageelongated barrel 15. Rotation of locking knob 26 may impose a load onelongated barrel 15 to establish a threshold torque for rotating knurledrotation knob 22. Alternatively, locking knob 26 may be rotated so thatteat 27 of set screw 25 effectively locks elongated barrel 15 in a givenangular orientation, and against further rotation.

Handle member 13 has a lower portion defining a finger or thumb hole andan upper portion 28 having longitudinal bore 29. Longitudinal bore 29aligns with longitudinal bore 21 in body portion 20 of handle member 12when handle members 12 and 13 are joined for relative movement at pivot14. Handle member 13 comprises a similar material as handle member 12,e.g., a cast aluminum alloy.

Drive rod 16 has a proximal end 30 disposed within elongated barrel 15and a distal end 31 engaged with working end 11. Proximal end 30 ofdrive rod 16 has electrical terminals 17 projecting from its endface 32,and a portion adjacent to endface 31 that defines a semi-circular groove33. Because drive rod 16 has a high electrical potential relative tohandle members 12 and 13 when electrical terminals 17 are connected to apower supply, drive rod 16 is electrically insulated from handle member13 and elongated barrel 15 by a coating of electrically insulatingmaterial disposed on the exterior surface of drive rod 16.

Groove 33 of drive rod 16 is captured in insulating disk 34 betweeninsulating pins 35. Insulating disk 34 seats in circular aperture 36 inupper portion 28 of handle member 13. Insulating disk 34 may comprise ahigh strength plastic, such as, Ultem (a proprietary plastic of theGeneral Electric Company, Fort Wayne, Ind., fabricated frompolyethermide), or a ceramic material. Longitudinal bore 37 extendsthrough insulating disk 34 in alignment with longitudinal bore 29 ofupper portion 28, for accepting proximal portion 30 of drive rod 16.Insulating disk 34 includes a pair of bores that perpendicularlyintersect bore 37, the pair of bores accepting insulating pins 35.Insulating disk 34 is capable of angular movement in circular aperture36, when handle member 13 rotates relative to handle member 12 aboutpivot 14.

Insulating pins 35, which may comprise a sturdy electrically insulatingmaterial such as ceramic or anodized aluminum, engage groove 33 in driverod 16 so that the drive rod 16 is capable of rotating about itslongitudinal axis, but cannot move transversely with respect toinsulating pins 35. Accordingly, drive rod 16 is mounted to handlemember 13 for rotation about its longitudinal axis in insulating pins 35and for transverse motion with respect to handle member 12 by virtue ofangular movement of insulating disk 34 in aperture 36.

Referring now to FIG. 3, a scissors-like embodiment of working end 11 isdescribed. The distal end of elongated barrel 15 has diametricallyopposed U-shaped slots 38 extending proximally from distal endface 39.Apertures 40 in the distal end of elongated barrel 15 are aligned acrossthe diameter of the barrel to accept insulating pivot pin 41.

Proximal end 31 of drive rod 16 comprises semi-circular halves 16', eachhalf 16' having an indentation 42 extending inward from its distalendface 43. Indentations 42 of halves 16' oppose each other to create aslot in the distal end of drive rod 16 within which the shanks of themovable members of working end 11 are disposed. Halves 16' have layer 45of insulating material disposed on contacting surfaces 44, so that nocurrent passes through those contacting surfaces. Layer 45 of insulatingmaterial also covers the outer surfaces of drive rod halves 16' toprovide electrical insulation between drive rod 16 and elongated barrel15. No insulation is provided on the interior surfaces of indentations42, so that the interior surfaces of indentations 42 are in electricalcontact with the shanks of the movable members. Insulating drive pin 46extends through apertures 47 near the endfaces 43 of halves 16'.

An alternative embodiment of the drive rod is illustrated in FIG. 4,wherein drive rod 16 comprises drive member 70 carrying electrodeassembly 71. Electrode assembly 71 in turn comprises semi-circularelectrode halves 72 separated by insulating strip 73. Insulating strip73 extends from the distal end of drive member 70 to a position near theshanks of the movable members to form a slot in the end of drive rod 16for accepting the shanks of the movable members of working end 11. Theinner surfaces of electrode halves 72 need not include a layer ofinsulating material, because insulating strip 71 serves to electricallyisolate the electrode halves from each other.

The outer surfaces of electrode halves 72 are coated with anabrasion-resistant electrically insulating material 45' thatelectrically isolates the electrode halves from elongated barrel 15.Insulating material 45' may comprise, for example, Teflon or polyimide.Insulating drive pin 46 extends through apertures 47' located near thedistal endfaces 43' of the electrode halves, as in the previouslydescribed embodiment.

Still referring to FIG. 4, electrode halves 72 are affixed to eitherside of insulating strip 73 by insulating pins 74. Insulating pins 74extend through apertures 75 in electrode halves 72 and apertures 76 ininsulating strip 73, respectively. Insulating pins may comprise a sturdyelectrically insulating material, for example, ceramic or anodizedaluminum.

The proximal end of insulating strip 73 is inserted into slot 77 in thedistal end of drive member 70. In this embodiment, drive member 70,which comprises the major portion of drive rod 16, may comprise a sturdyelectrically insulating material, such as Teflon or nylon. Drive membermay then be formed, for example by extrusion, having two bores 78 toaccept electrical connectors 79 projecting from the proximal faces ofelectrode halves 72. Bores 78 may then contain electrical leads thatconnect electrode halves 72 to electrical terminals 17 projecting fromthe proximal end of drive rod 16.

The proximal end of insulating strip 73 is affixed to the distal end ofdrive member 70 by pins 80. Pins 80 extend through apertures 81,provided for that purpose adjacent the slot 77 in drive member 70, andapertures 82 in insulating strip 73, respectively. Pins 80 comprise asturdy electrically conducting or insulating material, inasmuch as pins80 do not form a part of the electrical circuit of instrument 10. Thus,pins 80 may comprise, for example, either stainless steel or alumina.

For the illustrative embodiment shown in FIGS. 1-5, working end 11 ofinstrument 10 includes first and second members 18 and 19. First andsecond members 18 and 19 comprise scissor halves pivotally connected byinsulating pivot pin 41. Tube insulator halves 48 are disposed adjacentto the exterior surfaces of members 18 and 19 to electrically insulatethose members from elongated barrel 15. Insulating pivot pin 41 has itsends flush with the outer surface of elongated barrel 15 and extends,from side to side, through a first tube insulator half 48, members 18and 19, and a second tube insulator half 48.

Insulating pivot pin may comprise an electrically insulating metallicpin, e.g., anodized aluminum, having its ends deformed by peening.Alternatively, insulating pivot pin 41 may comprise a rod-like memberhaving a threaded recess at either end to accept a screw. The screwsengage the threaded recesses and permit an adjustable compressive loadto be applied to elongated barrel 15, and hence members 18 and 19.

Members 18 and 19 include, respectively, shearing surfaces 50 and 60,cutting edges 51 and 61, exterior surfaces 52 and 62, apertures 53 and63, and shank portions 54 and 64. A thin layer 49 of insulating coatingis provided on one or both of the opposing mating surfaces of members 18and 19, including one or both of the shearing surfaces 50 and 60, andone or both of the mating surfaces of the shank portions 54 and 64.

Members 18 and 19 are configured to constitute the individual electrodesof a bipolar electrode instrument, as described in copending andcommonly assigned U.S. patent application Ser. No. 07/877,703, filed May1, 1992, now U.S. Pat. No. 5,324,289, the disclosure of which isincorporated herein by reference. That application describes a firstfamily of embodiments wherein the opposing scissor halves are made of anelectrically conducting material and serve as both the electrodes andshearing surfaces. That application also describes a second family ofembodiments wherein the opposing scissor halves are made of anelectrically insulating material and have electrically conductiveportions disposed on the exterior surfaces of the scissor halves.

For the scissors-like embodiment of the working end shown in FIGS. 1-5,members 18 and 19 may be constructed of metallic alloys that offer goodelectrical conduction, adequate hardness and tensile strength sufficientto allow the members to be oriented toward each other to effect adequatewiping at the cutting edges. Materials having these characteristicsinclude stainless steel, e.g., 301, 302, 304 and 316, martensiticstainless steels, e.g. 410, 420, 430 and 440, and precipitation hardenedsteels, e.g., 17-4PH and 17-7PH alloys. The use of such materials permitmembers 18 and 19 to be formed by numerous methods, including forgingfollowed by machining, die casting, metal injection molding, andelectrodischarge machining (EDM) cut-out of the features.

Layer 49 of insulating coating covers the inside face of one or both ofcutting edges 51 and 61, so that the cutting edges are electricallyisolated from each other. Thus, current flows between exterior surfaces52 and 62 of members 18 and 19 in the region near cutting edges 51 and61, while ensuring that members 18 and 19 do not electrically contacteach other within the range of the cutting or opening motion of themembers. Consequently, hemostasis of tissue occurs at a location just inadvance of the cutting point while cutting edges 51 and 61simultaneously sever the hemostatically heated tissue, as described inthe above-referenced U.S. patent application Ser. No. 07/877,703, nowU.S. Pat. No. 5,324,289.

Because shank portions 54 and 64 move through a range of motion whereinthe opposing mating surfaces of shank portions 54 and 64 move acrosseach other, layer 49 disposed on one or both of the opposing matingsurfaces of the shank portions prevents electrical shorting betweenthose surfaces. Thus, layer 49 electrically isolates shank portions 54and 64 in the same manner that it electrically isolates shearingsurfaces 50 and 60. Alternatively, layer 49 need not be be disposed onthe interior surfaces of one or both shank portions 54 and 64, but maycomprise an electrically insulating washer disposed, for example, oninsulating drive pin 46 between shank portions 54 and 64, therebyseparating the shank portions.

Referring again to FIG. 3, shank portions 54 and 64 of members 18 and 19include angled slots 55 and 65. The exterior surfaces of shank portions54 and 64 contact the interior surfaces of halves 16' at indentations42. Since the interior surfaces of indentations 42 are not covered byinsulating material 45, halves 16' are in direct electrical contact withshank portions 54 and 64.

Members 18 and 19 and drive rod halves 16' are constructed of a metallicmaterial that provides good electrical contact, such that the slidingcontact resistance of each member 18 and 19 and its respective drive rodhalve 16' is less than 5 ohms, and preferably less than 1 ohm. Theinterior surfaces of indentations 42 and the exterior surfaces of shankportions 54 and 64 may be gold plated to reduce the sliding electricalcontact resistance.

Accordingly, the electrical circuit energizing each bipolar electrodeextends from electrical terminals 17 on the proximal portion 30 of driverod 16, through halve 16' of drive rod 16 to proximal portion 31 ofhalve 16'. The outwardly disposed shank portion of the respectivemembers 18 and 19 are in sliding electrical contact with the interiorsurfaces of indentations 42 of each of drive rod halves 16', therebyproviding a voltage potential across the tissue contacting portions ofworking end 11. Insulating layer 45 (or insulating strip 73 of theembodiment of FIG. 4) electrically isolates halves 16' (or electrodehalves 72), while layer 49 of insulating material on one or both ofmembers 18 and 19 electrically isolates those members, as describedheretofore.

Insulating drive pin 46 extends through slots 55 and 65 of shankportions 54 and 64. The ends of insulating drive pin 46 are disposed inapertures 47 of drive rod halves 16' so that they do not interfere withreciprocatory movement of drive rod 16 in elongated barrel 15.Insulating pin 46 may be comprised of, for example, silicon nitride,zirconia, alumina, or other material which has the mechanical strengthto withstand the loads imposed on the pins during opening and closing ofmembers 18 and 19, while providing the requisite electrical insulationbetween shank portions 54 and 64.

As shown in FIGS. 5A and 5B, slots 55 and 65 are configured so that whenthe handle members are actuated to urge drive rod 16 in a distaldirection, insulating drive pin 46 is urged to the distal ends of slots55 and 65, thereby opening members 18 and 19 (see FIG. 5A). In thisfirst position, working end 11 may be positioned so that members 18 and19 are located proximate to the tissue, without imposing any mechanicalload thereon.

On the other hand, when handle members 12 and 13 are rotated towardseach other, drive rod 16 is reciprocated proximally. This motion pullsdrive pin 46 toward to the proximal ends of slots 55 and 65, therebyclosing members 18 and 19 as shown in FIG. 5B. As members 18 and 19 aregradually closed, the cutting point defined by the intersection ofcutting edges 51 and 61, moves along those cutting edges, so that acurrent flows through the tissue to cause hemostasis of the tissueimmediately prior to its being severed mechanically. Thus, in thissecond position, hemostasis is achieved in the tissue by the currentflowing between members 18 and 19, and then mechanically severed.

Layer 49 of electrically insulating material may have a hardness that isgreater or substantially greater than the steel or other electricallyconducting material used to manufacture conventional scissors-likedevices. For example, members 18 and 19 may be made of a martensiticstainless steel, e.g., AISI 420. Insulating layer 49 may then comprise,for example, a ceramic material such as alumina or zirconia, that isdeposited on shearing surface 52 of member 18 by conventional plasma orflame-sprayed deposition techniques. The applied coating forms anon-conductive cutting edge for that member and has a greater hardnessthan the steel substrate and the steel of opposing member 19.Consequently, as layer 49 rubs against the cutting edge 61 or shearingsurface 60 of member 19, steel shearing surface 60 and cutting edge 61are mechanically ground or polished by the harder insulating layer 49.Cutting edges 51 and 61 are therefore self-sharpening and remain sharpduring continued use.

Insulating layer 49 has a thickness in the range of 0.002 inches toabout 0.050 inches, more preferably 0.003 to 0.007 inches. The applicanthas determined that at thicknesses 0.001 inch or less, the thickness ofthe insulating layer 49 is insufficient to prevent shorting of theelectrodes. Insulating layer thicknesses above 0.002 inches and below0.050 inches cause adequate hemostasis. It has been observed, however,that the greater the minimum distance between the proximate currentconducting portions of the opposing electrodes in the region of currentflow through the tissue, the longer the current path through the tissueand the more difficult it becomes to obtain the desired localized andintense heating to achieve adequate hemostasis. Insulating layerthicknesses above 0.050 inches are believed to be too large for mostpractical applications, for the ceramic insulating materials described.

FIG. 6 shows an alternative embodiment of the working end of FIGS. 5Aand 5B, in which like numbers designate similar elements. The embodimentof FIG. 6 differs from that of FIGS. 5A-B chiefly in that the cuttingedges 51 and 61 are curved rather than straight, and member 19 is fixedrelative to the longitudinal axis of elongated barrel 15. Thus,reciprocatory movement of drive pin 46 moves member 18 between the openand closed positions. Curved cutting edges 51 and 61 ensure that thetissue to be severed does not slip from between members 18 and 19 duringthe cutting action, thereby providing enhanced precision in cuttingtissue.

Referring now to FIGS. 7A and 7B, an alternate embodiment of working end11 of the present invention is described, in which like-primed numbersdesignate similar elements. Jaw-like members 18' and 19' have shankportions 54' and 64', respectively. Shank portions 54' and 64' in turnhave angled slots 55' and 65', respectively. Insulated drive pin 46'extends through slots 55' and 65' and has its ends secured in apertures47' of indentations 42'. Members 18' and 19' have grasping surfaces 50'and 60', teeth 51' and 61', and exterior surfaces 52' and 62',respectively. Teeth 51' and 61' are disposed in opposing relation ongrasping surfaces 50' and 60' to grasp tissue captured between members18' and 19'. Alternatively, the grasping surfaces may include a patternof pyramidal teeth that serve to grasp the tissue.

As for the embodiment of FIGS. 5A and 5B, members 18' and 19' of thedevice of FIGS. 7A-B comprise the electrodes of a bipolar device. A thinlayer 49' of insulation may be disposed on one or both of the matingsurfaces of shank portions 54' and 64' to prevent electrical shortingbetween members 18' and 19' when those members are moved between theopen and closed positions. Alternatively, layer 49' may comprise aninsulating washer disposed on insulating drive pin 46 between the shankportions to electrically isolate shank portions 54' and 64'.

Layer 49' of insulating material may in addition cover the opposingsurfaces of teeth 51' and 61' of the respective members. Alternatively,teeth 51' and 61' may be dimensioned so that when the members are in theclosed position, a gap exists between teeth 51' and 61' sufficient toprevent direct shorting between the members.

Actuation of the handle members of the instrument urges drive pin 46' tomove members 18' and 19' from a first position where the members can bedisposed around a mass of tissue, to a second position where the membersgrasp the tissue. Members 18' and 19' therefore move through agraspers-like range of motion, similar to that of a conventional pliers.In the second position, current flows between members 18' and 19' toachieve hemostasis of the tissue captured therebetween.

Exterior surfaces 52' and 62' of members 18' and 19' may have a smooth,rounded, cross-section to facilitate blunt dissection. For example, suchan instrument may be inserted--with members 18' and 19' closedtogether--into an incision made in a multilayer tissue mass. In thisfirst position, the tissue merely contacts the outer surface of members18' and 19', without imposing a substantial mechanical load thereon.

The electrodes may then be energized, and jaw-like members 18' and 19'may be gradually opened to separate the layers of tissue whilesimultaneously causing hemostasis of the tissue. When members 18' and19' are moved to this second position, the outer surfaces of the membersengage the tissue and separate the tissue layers along tissue boundarieswithout severing.

FIG. 8 shows an alternative embodiment of the working end of FIG. 7, inwhich the tips of members 18' and 19' are curved so that they lie in aplane parallel to the longitudinal axis of elongated barrel 15'. Becausethe endoscope is typically inserted into the surgical area adjacent tothe surgical instrument, the parallax resulting from the acute angleformed between the endoscope and the surgical instrument may restrictthe surgeon's view of the surgical site. Thus, the surgeon may have onlya limited view of the working end of the surgical instrument.

The embodiment of FIG. 8, however, resolves this difficulty by enhancingthe surgeons's view of the working end of the instrument. Providing acurved working end, so that its tips lie in a plane parallel to thelongitudinal axis of elongated barrel 15', enhances the precision of thesurgical procedure. Of course, it will be apparent to one skilled in theart that any of the previously discussed embodiments of working end 11of the present invention similarly could be provided with curved tips toenhance the surgeon's field of view. To ensure that the working end ofthe instrument will pass easily through standard trocar tubes, the tipsof members 18' and 19' should not extend beyond the diameter ofelongated barrel 15.

In addition to the above-described endoscopic bipolar instruments, thepresent invention includes use of such instruments in combination with apower supply providing a substantially constant voltage at selectableoutput levels, wherein the voltage output is independent of the loadimpedance. Such devices are described, for example, in U.S. Pat. Nos.4,092,986 and 4,969,885.

To reduce coagulum buildup on the working surfaces of the scissors,applicant has developed power supplies providing substantially constantvoltage output that is independent of the load impedance, low sourceimpedance and a alternating-current voltage waveform having a crestfactor--the ratio of peak voltage to RMS voltage--near unity. Thesepower supplies are described in copending and commonly assigned U.S.patent application Serial No. 07/877,703, now U.S. Pat. No. 5,324,289.The present invention, when powered by such experimental power supplies,has been observed to provide highly satisfactory hemostasis withoutarcing or charring of the tissue, and little coagulum buildup.

The present invention includes the method steps of employing anapparatus having movable members that include electrodes with aninterposed layer of insulating material, wherein operation of theapparatus simultaneously manipulates and causes hemostasis of thetissue. Applicant has observed that use of apparatus constructed inaccordance with the principles of this invention provides good results,with little sticking or coagulum accumulation, when used in conjunctionwith a power supply having a load-independent substantially constantvoltage output. Frequencies in the range of 100 kHz to 2 MHz andvoltages in the range of 10 to 120 volts (RMS) (across the bipolarelectrodes) have been determined to provide highly satisfactoryperformance under a wide range of conditions.

The method of the present invention, suitable for use in performing agreat variety of endoscopic surgical procedures on a patient's internaltissue, comprises the steps of:

(a) providing an instrument having an elongated barrel, actuating means,and a working end comprising first and second members movable betweenfirst and second positions, the first and second members having opposingmating surfaces that move across each other when the first and secondmembers are moved between the first and second positions, each of thefirst and second members having an electrode associated therewith;

(b) providing an electrically insulating material between the first andsecond electrodes so that the electrodes do not contact each other whenthe opposing mating surfaces move across each other;

(c) connecting the electrodes to a power supply;

(d) incising the patient's tissue with a trocar or similar device tocreate a small opening into the patient's body cavity;

(e) inserting the working end and elongated barrel of the instrumentthrough a trocar tube so that the working end is disposed adjacent tothe internal tissue;

(f) selecting and maintaining a substantially constant voltage leveloutput across the power supply, the voltage level output independent ofthe load impedance;

(g) placing the electrodes in electrical contact with the tissue; and

(h) operating the actuating means to move the first and second membersbetween the first and second positions to simultaneously manipulate thetissue and cause hemostasis of the tissue by passing a currenttherethrough.

Of course, it will be apparent to one skilled in the art that steps (a)and (b) described above can be combined by simply providing an apparatusas hereinbefore described. Operation of the apparatus in the range 10 to90 volts (RMS) is desirable in many cases, depending upon the impedanceof the tissue encountered during the surgical procedure. Of course, oneskilled in the art will also recognize that the above-stated voltagesare those imposed across the electrodes of the bipolar instrument,rather than the output terminals of the power supply, since allowancemust be made for line losses encountered in the cables connecting theelectrosurgical instrument to the power supply.

The use of a power supply having a selectable substantially constantvoltage level output that is independent of load impedance providessufficient power to cause effective hemostasis. Use of voltage outputlevels lower than those generally used in previously knownelectrosurgical instruments reduces the power delivered to theelectrodes when they are not in contact with tissue, i.e.,open-circuited, and reduces the likelihood of generating a current arcwhen the electrodes are brought into contact with the tissue.

Use of a constant voltage level output that is independent of the loadimpedance inhibits excessive current flow through the tissue, as thetissue resistance increases during desiccation. Consequently, the depthof hemostasis obtained within the tissue can be more preciselycontrolled, and localized overheating of the electrodes better avoided.Reduced localized heating of the electrodes also inhibits coagulumbuildup, which can both interfere with efficient hemostasis and impedemaneuverability of the instrument.

The various embodiments described herein are presented for purposes ofillustration and not limitation, as the present invention can bepracticed with endoscopic surgical instruments of any type having twoopposing members movable with respect to one another. The instrumentsand methods of the present invention may be adapted, as may be required,for use in operating on any internal tissue, vessel, or organ.

For example, the present invention may be practiced using an actuatingmeans comprising a pistol style grip having a spring-biased trigger toreciprocate drive rod 16, rather than the handle members describedhereinbefore. One skilled in the art will appreciate that the presentinvention can be practiced by other than the described embodiments, andthat the present invention is limited only by the claims that follow.

What is claimed is:
 1. A method of endoscopically manipulating andcausing hemostasis of a patient's internal tissue, the method comprisingthe steps of:providing an instrument having an elongated barrel,actuating means, and a working end comprising first and second scissormembers, the first and second scissor members including first and secondscissor blades having first and second cutting edges, respectively, thefirst and second scissor members electrically insulated from one anotheralong the first and second cutting edges and pivotally joined so that atleast the first scissor blade moves relative to the second scissor bladein a scissors-like cutting motion, wherein the first and second scissorsblades close together for shearing tissue located therebetween;connecting the instrument to a power supply that provides a highfrequency alternating-current waveform; incising the patient's tissuewith a trocar or similar device to create a small opening into thepatient's body cavity; inserting the working end and elongated barrel ofthe instrument through a trocar tube so that the working end is disposedadjacent to the internal tissue; placing the first and second scissorsblades to locate internal tissue therebetween; and operating theactuating means to move the first scissors blade relative to the secondscissor blade to sever tissue located therebetween and so a currentflows between the first and second scissor members across the first andsecond cutting edges and through the internal tissue to cause hemostasisthereof.
 2. The method of claim 1 wherein the step of providing aninstrument comprises selecting an instrument wherein at least one of thefirst and second scissor members is formed of a composite of a metallicmaterial and an insulative material that electrically insulates thefirst and second scissor members from one another, the insulativematerial forming a layer having a thickness in a range of 2 to 50 mils.3. The method of claim 1 wherein the step of providing an instrumentcomprises selecting an instrument wherein both the first and secondscissor members are each formed of a composite of a metallic materialand an insulative material that electrically insulates the first andsecond scissor members from one another, the insulative material of thefirst and second scissor members having a combined thickness in a rangeof 2 to 50 mils.
 4. The method of claim 1 further comprising the step ofsetting the power supply to provide an alternating-current voltagewaveform with a frequency in a range of 100 kHz to 2 MHz.
 5. The methodof claim 1 wherein the step of connecting the apparatus to a powersupply that provides a high frequency alternating-current waveformcomprises the step of selecting and maintaining a constant voltage levelacross the first and second scissor blades.
 6. The method of claim 5wherein the step of selecting and maintaining a constant voltage levelcomprises selecting the voltage level from a range of 10 to 120 voltsRMS.
 7. A method of endoscopically manipulating and causing hemostasisof a patient's internal tissue, the method comprising the stepsof:providing an instrument having an elongated barrel, actuating means,and a working end comprising first and second shearing members, thefirst and second shearing members including first and second shearingsurfaces, first and second cutting edges, and first and secondelectrodes located adjacent to the cutting edges, respectively, thefirst and second shearing members having a length, and a layer ofinsulative material disposed upon at least one of the first and secondshearing surfaces to electrically isolate the first and second cuttingedges from one another, the first and second shearing members pivotallyconnected so that the first shearing surface moves relative to thesecond shearing surface in scissors-like cutting action; providing apower supply providing a high frequency alternating-current waveform;connecting the electrodes to the power supply; incising the patient'stissue with a trocar or similar device to create a small opening intothe patient's body cavity; inserting the working end and elongatedbarrel of the instrument through a trocar tube so that the working endis disposed adjacent to the internal tissue; placing the first andsecond shearing members to locate internal tissue therebetween; andoperating the actuating means to move the first and second shearingmembers so that the first and second cutting edges close together toshear the internal tissue located therebetween and to pass a currentbetween the first and second electrodes through the internal tissue andacross the first and second cutting edges sufficient to cause hemostasisof that tissue.
 8. The method of claim 7 further comprising the step ofsetting the power supply to provide an alternating-current voltagewaveform with a frequency in a range of 100 to 2 MHz.
 9. The method ofclaim 7 wherein the internal tissue has multiple layers, the methodfurther comprising the steps of:inserting the working end of theinstrument into the multiple layers of internal tissue with the firstand second shearing members closed together and so that the first andsecond electrodes contact the internal tissue; and wherein the step ofoperating the actuating means causes the first and second members toopen, so that the multiple layers of internal tissue are simultaneouslyseparated and hemostasis of the internal tissue is achieved.
 10. Themethod of claim 7 wherein the step of providing an instrument comprisesselecting an instrument having a layer of insulative material disposedon the first shearing surface with a thickness in a range of 2 to 50mils.
 11. The method of claim 7 wherein the step of providing aninstrument comprises selecting an instrument having a layer ofinsulative material disposed on each of the first and second shearingsurfaces having a combined thickness in a range of 2 to 50 mils.
 12. Themethod of claim 7 wherein the step of providing a power supply providinga high frequency alternating-current waveform comprises a step ofselecting and maintaining a constant voltage level across the first andsecond electrodes.
 13. The method of claim 12 wherein the step ofselecting and maintaining a constant voltage level comprises selectingthe voltage level from a range of 10 to 120 volts RMS.